1. Field of the Invention
This invention relates to dash pot devices in general, and more particularly to a dash pot device applied to a deceleration control system of automobile engines.
2. Discussion of the Background
It is generally known that upon engine deceleration a great quantity of hydrocarbon(HC) and/or carbon oxidide(CO) gases are discharged owing to imperfect combustion and misfiring which are caused by a rich air-fuel ratio and a lowering of volumetric efficiency. Accordingly, there have been introduced several kinds of engine deceleration control devices which prevent HC,CO gases from being discharged from the engine. In a dash pot device, such being one of such devices, when a carburetor throttle valve returns to an engine idle speed portion on the engine deceleration, the return action of the throttle valve is delayed by means of a buffer action of a dash pot. Thus, the throttle valve gradually returns to the idle speed position to thereby prevent the occurrence of a rich air-fuel ratio and misfiring.
A conventional dash pot device is shown in Japanese Patent Publication No. 50(1975)-12540 wherein a labyrinth groove passage is used as a delay mechanism which delays the return action to the engine idle speed position of the throttle valve. The delay capacity of the labyrinth groove passage is much smaller than that of a pinhole type orifice passage. If the pinhole type orifice passage is used as the delay mechanism, however, loading of the pinhole orifice passage cannot be avoided. Furthermore, the above dash pot device includes an air filter so as to prevent foreign matter from entering into a diaphragm chamber. Since the air filter is positioned so as to be exposed to the atmosphere, it may be necessary to take into consideration the positioning direction of the dash pot so as to avoid loading of the air filter which is caused by muddy water within the engine compartment.